Classifier



H. G. LYKKEN 2,258,901

Oct. 14, 1941.

. CLASSIFIER Filed May 29*. 1957 s Sheets-Sheet 1 Oct. 14, 1941. H. G.LYKKEN 2,258,901

CLASSIFIER Filed May 29, 1937 3 Sheets-Sheet 2 INVENTOR. Henry 6.Ay/f/ferp ATTORNEY. I

Oct. 14, 1941. H. a. LYKKEN CLASS IFIER F-iled May 29; 1937 5Shets-Sheet 3 INVENTOR. H 227 6 Ay/f/fen BY// ATTORNEY.

Patented Oct. 14, 1941 CLASSIFIER Henry G. Lykken, Minneapolis, Minn.Application May 29, 1937, Serial No. 145,496

19 Claims.

This invention concerns improved machines and methods for classifyingthe particles of a mass of previously pulverized material, wherebymaterial of a predetermined particle size may be segregated from themass and delivered from the machine, or material of several differentparticle sizes may be delivered from the machine separately andconcurrently. The machine is not intended to have any pulverizingaction, although it is recognized in some of the suggested forms minorand incidental pulverizing will occur.

In the present machine the mass of pulverized material after beingintroduced into the machine is caught in a rising vortex of gaseousmedia, such as air, and is whirled around in a classifying compartmentat high speed, care being exercised to prevent any disturbing forces,eddyor other currents. The gaseous media and pulverized material mayenter the classifying compartment in many different ways and thereafter,ac-

cording to the present invention, is maintained in the vortex state by ahigh speed, smooth rotor which, together with an oppositely disposedconcentric, stationary wall of the machine, defines a narrow, vertical,annular classifying space.

The centrifugal force of the vortex action on the particles effects theclassification or sorting of the material in accordance with thedifferences in size and corresponding mass velocities of the variousmoving particles in the classifying zone. That is, the finer particlesbeing of small mass are less affected by the centrifugal forces set upby the vortex action, and consequently rise at and near the innerperiphery of the vortex to a place ofexit adjacent the top of themachine. The larger particles are projected outwardly toward the outerperiphery of the vortex during their rise in the classifying spacebetween the rotor and the opposite wall, and the respective sizes riseto define heights or places along the outer wall according to theirsizes, as will be more fully explained hereafter. Consequently, inaddition to the very fine particles, it is possible to take out of theclassifying chamber and collect particles of any larger size, or ofdifferent graded sizes, by suitably locating a tapping zone or zonesverticallly of the circumferential wall of the classifier. It is, ac-

' cordingly, one object of this invention to provide means forefiiciently effecting any or all of the abovepurposes.

The machine of this invention is capable of classifying various kinds ofpulverized materials whether they be of uniform chemicalcharactertrained material. classified may also enter the machine withthe aggregates, etc. Furthermore, the classifier of this application maybe used with various types of pulverizing machines.

The air or other gaseous media may be let into the machine from a placebeneath the rotor, or near the bottom of the machine, and may also beinduced to rise through the classifying chamber by means of a suitablefan adjacent the'top of the machine, or by appropriate exhaust meansconnected to an outlet from the classifying chamber. However, careshould be exercised that such devices do not disturb or agitate thesmooth movement of the rising currents of air and en- If desired, thematerial to be air. As another instance, the material may be fedtangentially through the wall of the classifying chamber either with orwithout the necessary air to form the carrier. As a further example, asuitable mechanical feeding means, such as a screw conveyor may be used,in which case the air may be fed into the classifying chamber from thebottom or tangentially, or both,

. as may be found advisable in accordance with operating conditions andthe particular materials to be dealt with.

By whatever means thematerial and air en- I ter the classifying chamber,unless thematerial enters the machine with a sufliciently vorticalmotion and in substantial suspension in the air, it is quickly put intosuspension and the air and mass of suspended particles caused to Whirlby the action of the high speed rotor. In the drawing the rotor isprovided at its lower end only with spaced apart vertical fins or othersuitable means for originating the vortex.

It is another object of this invention to pro vide a classifier with,vanes or similar means to initiate a vortex action, and a smooth rotorelement for maintaining the vortex action.

It is still another object of this invention to provide a classifier ofthe above indicated character wherein the-classification zone hasuninterrupted, smooth, continuous currents of air and entrainedmaterial. v

In some industries abrasive materials having particles of uniformsize-are required. This is the case in the manufacture of brake bandswhere the abrasive particles in some instances must approximate 30microns. In other fields it is important that the material have no metalcontamination as for example the cosmetics or food industries. Inhandling all these materials the parts of the machine may be protectedas by istics, or are compounds, or various forms of having the movingand stationary walls of the classifying chamber covered withresilient-material such as rubber. The rubber increases what might betermed a skin-drag effect on the air with two results, first, reducingthe wear on the walls and rotor parts, and, second, the rubber coveredrotor will move more air, thereby increasing the vortex action, withoutsetting up undesired undulating or eddy currents, all ofwhich isconducive to speedy and accurate classification. Furthermore, the rubberfacing of the stationary wall has a retarding action on the particlesmoving therealong and slows or stops their motion somewhat definitely,and also preventing the deflection and return of the particles to thevortex.

It is, therefore, a further object of this invention to provide rubberor other similar walls along the classification zone.

At times, to obtain accurate classification it may be desirable toconnect two or more classifiers in series relation so that the materialis returned one or more times through classifying zones for furthergrading. With this arrangement, the oversize and undersize particles areboth eliminated to obtain a substanially uniform final product. Hence,it is a still further object of this invention to provide a method andarrangement of apparatus for accomplishing the abovementioned result.

Various other objects and advantages of the invention will appear as thedescription proceeds, reference being made to the accompanying drawings,illustrating several practical embodiments of the invention, and inwhich Figure 1 is a vertical sectional view of a classifying machine"constructed in accordance with the invention, parts being broken away tofacilitate the illustration;

Fig. 2 is a horizontal cross sectional view taken in the planeofline2--2 of Fig. 1;

Fig. 3 is a fragmentary view in vertical section of a classifyingmachine illustrating a modified form of device having a plurality oftapping points at the side of the machine, and also showing theapplication of rubber linings to the classifying chamber;

Fig. 4 is-a'view in vertical section of a portion of a classifyingmachine illustrating a modified form of tapping arrangement at the sideof the classifler andalso showing one form of conveyor-for feedingpulverized material to the machine; a

Fig. 5 is a fragmentary view of a classifier constructed according tothe invention and illustrating the approximate paths taken along theclassification chamber by the various sizes of particles, the spiralportion of the paths being omitted; and

Fig. 6 is a diagrammatic illustration of apparatus for and method ofsubjecting the particles one or more times to the action of aclassifying zone for further gradation.

Referringto the drawings, and more particularly to Figs; 1 and 2, themachine comprises-in general a-stationary, vertical, generally"cylindrical casing or housing It], a drum-like rotor ll mounted on avertical shaft I2 for concentric rotation in the housing at high speed,the shaft being mounted in top and bottom bearings l3 and I4respectively. The elongated space l5 defined between the rotor II andthe oppositewall of the casing 10 forms a classifying chamher or zonefor the pulverized material, which may be continuously fed to thischamber in a variety of ways.

If desired, the pulverized material, together annular space about therotor H. Air also may be fed into the classifying chamber I 5 at thebottom of the rotor H through a central opening in a base plate [8 andthrough an annular air-seal opening l9 which communicates with the airsupply through an inlet opening 20 in the base of the machine.. Therotor ll revolving at high speed sets up, or continues as the case maybe, a vortex in the material-laden air. A fan I! mounted at the upperend of the shaft l2, or an exhaust fan (not shown) connected to themachine outlets also may induce the particles of thematerial and thesupporting air currents to rise in the chamber l5 during the whirlingaction of the vortex. In cases where the bottom feed of air is used theair will rise through the classification zone, and the fan l1 may beconsiderably reduced in proportions or eliminated.

In cases where pulverized material is fed into the classifier withinsufficient force, etc., it becomes necessary to initiate the vortexaction quickly and in sufficient intensity, and in other cases where itis desired to more quickly set up the vortex action in the classifyingchamber, the lower portion of the rotor H may be provided with spacedblades or fins 2|. These blades are secured to the face of the drum orrotor, and are tapered with the wide portion moving very close to thebottom 18.

In all of the embodiments of the invention described in this applicationthe details of construction of the apparatus may be substantially thesame as that shown in Fig. 1. There the casing I0 is provided with acover plate 31, to which is fastened the upper bearing member l3,

. and a base 38 which also supports the lower bearing l4. The rotor llmay be mounted on the shaft l2 through the medium of upper and lowerannular heads 39 and 40 the upper head 39 beingbolted at 4! to a collar42 keyed as at 43 to the shaft l2; The rotor l I is of sheet metal, suchas polished Monel metal, and is mounted between the plates 39 and 40 soas' to form a smooth unbroken surface, especially in the upper portion.The fan or air impeller I! is also secured to the collar 42 by the bolts4|.

The shaft l2 may be driven by a -pulley and belt drive 44 from a motor45, or may be directly connected to the motor. For ordinary purposes aspeed of about 300 feet per second at the periphery of the rotor hasbeen found satisfactory, but this as well as the rate of air input andthe feed of the material may be varied according to the material andsizes being classified and can be regulated readily to bring about thedesired results hereinafter described.

The fan I] is mounted in a discharge chamber separated from theclassification chamber l5 by an annular plate 23 having 'a centralopening 22 of less diameter than the rotor, the arrangement being suchthat undulations or irregular movements of the air due to the rotationof the fan bllades will not be felt in the classification zone 5.

The plate 23 is spaced above the rotor top plate Accordingly, owing tothe confined'space and the ing on the particle.

; horizontal direction,

a vertical direction, of gravity and the .rising component resultingfrom Thus the larger particles are the other factors, a uniformclassification can be had of the smallest of the pulverized .particlessupplied to the classifier, or, if desired, of all particles below acertain size.

Considering the bottom portion in more detail, the air-seal opening I8is formed between the bottom edge of .the annular head 40 and the baseplate l8. Adjacent the opening l9'is a set of air-impeller blades 41-which function somewhat like an air pump to supply air evenly and underpressure all around the bottom of the classification chamber at .thebase of the fins 2|. The number and spacing and shape of the blades 41may be varied without affecting the efficient operation of the machine,and in some cases they may be eliminated, for instance, if the air wereforced into the machine under pressure through the inlet 20.

The lower portion of the classification chamber below the majorclassification zone may be characterized by an outer wallinclinedoutwardlytoward the bottom of the chamber as indicated at 48.This inclined wall cooperates with the outer edges of the blades 2|arranged at a. slightly greater inclination to form a tapered annularspace the effect width of which becomes narrower as it approaches thebottom. With this arrangement, the centrifugal forces acting on theparticles are increased at the bottom of the chamber due to the narrowedchamber and also the increased peripheral speed of the, bottom of thetapered blades 2|. Hence, the larger or oversize particles of material,falling to the bottom by gravity, are more quickly eliminated from thevortex by being swept around adjacent the base plate Hi to the outerwall '48 of the classification chamber and thence out of the machinethrough the exit port 26. It may be noted that the somewhat conical wall48 also tends tov deflect downwardly the heavier particles thrownoutwardly by the mid and upper portions of the blades 2|, therebyfurther aiding theprocess of eliminating those particles from themachine. A reason for the taper and height of the blades M is togradually reduce and finally eliminate from the classification zoneelements producing disturbing pulsations in the material-laden air,after which .final classification begins, as will now be described.

The approximate path of the particles is spirally upwardly while theclassified position of a particle of given size is approximatelyrepresented by the vector line computed from the forces act- Such forcesinclude the mass-velocity of the particle according to the well knownformula (MW), which is a force in a and the opposed forces, in

the lifting action of the gaseous media on the particles in the vortex.

.During revolution of the rotor II the pulverized particles of materialto be classified are set in rapid whirling motion and. are thrownoutwardly toward the casing cording to their mass tion of the air or ofparticles toward the (MV while the lifting actop of the classifyingcham- III with different velocities acagainst the pull of gravity,

the fans tends to raise the.

'particle along' the line R-S, along the line R-S selected fifty micronsize her, and the force of gravity tends to draw the particlesdownwardly. For a given set of .conditions of speed of rotation, volumeof aspirating air, and the effect of theforces noted above, theseparation or Stratification of the particles occurs along somewhatdefinite lines corresponding to different heights, along the inner wallof the casing [0 apparently determined by the vector line or resultantof the forces named above. This is diagrammatically illustrated in Fig.5 for a number of particles of different microscopic sizes. Forparticles of screen mesh, for example, there is a point on the outeredge of the vortex adjacent the wall of the casing wherecentrifugalforce upon such particles is not sufficient to maintain theparticle in suspension and hence particles of that size will quicklymass and fall from that height.

The s'ame action occurs for particles of 200 screen mesh size, and of 50micron size for further examples, but the points of equilibrium of theforces for these and other smaller sizes are at higher levels along thewall of the classification chamber.

Insofar as it has been possible to determine'at the present time it isbelieved that the various points of equilibrium and Stratification ofthe particles may be computed by considering a particle of a given sizeunder a definite set of conditions at the lower portion of .the majorclassification zone, which point is designated bythe letter R. A 100screen mesh particle will move substantially along the path of line R-S,a 200 mesh particle along the line R-S a 300 mesh a fifty micronparticlethe line R,S and 'so on progressively with the smaller particlesfollowing closely the periphery of the rotor II and passing throughopening 22 in plate 23 and out of the machine through a port 24. Acollector of any suitable constructioncan be connected to port 24 tocollect the particles discharged therefrom.

It is apparent that at any one or more of the circumferential areas S, Setc., the particles of the respective sizes may be taken out of themachine by providing suitable tapping ports around the casing I0.Accordingly, as illustrated in Figs. 1 and 5 a ring oftapping ports 25(obviously shown exaggerated in size) may be provided to take out theparticles at the S level which, in this example, are of the order offifty microns.

With the exception of the smaller particles, at times termed fines,which leave the machine through the port 24, the other sizes than theparticles fall toward the bottom of the classification chamber, and areswept out of the machine through the tan- 'gentially disposed outlet 25.

material may be removed from the classifier sia 400, mesh sizemultaneously. One arrangement therefor is by providing a repetition oftapping ports 25 at different levels as shown in Fig. 3. It is clearthat any suitable number of circles of such ports may be provided andthat with this arrangement a number of different particle sizes may becollected at the same time from a single machine.

In Fig. 4 is shown a slightly different form of tapping constructioninvolving the same general principles. In this example, the diameter ofthe upper part of the casing I is enlarged as indicated at 21. Thisincrease in the width of the classifying space enables the particles totravel outwardly where gravity has asmaller MV force to overcome, thusthe desired particles more readily gravitate and find their waysubstantially straight downward and out of the machine through the portopenings 29 to a place of collection or use at the outside of themachine. It will be seen that with this form of device all particlesbetween the smallest, which escape through opening 22, and the sizedetermined by the height of the lip 28, will be collected so that amixture of graduated sizes will be available. Such mixtures are usablein a number of industries, of which the cement industry is one.

product. Unit A in Fig. 6, operating as any of the machines describedabove, has a circle of tapping ports I25 which discharge into the lowerportion of 'the classifying zone of unit B. The particle size at portsI25 may be fifty microns as assumed above, but some particles of smallersize also'may be ejected through ports I25. However, when thatdischarged material enters the B unit the desired fifty micron particlehas now become the largest particle size in the B unit. That particlesize may now be discharged and collected through bottom outlet I26 whilethe lighter material rises and is taken off at the top opening I35 orthrough an intermediate tap I31 as indicated.

While several practical embodiments of the invention have beenillustrated 'and described, it is to be understood that various othermodifications There is also shown in Fig. 4 a screw feed conveyor 30,provided with a suitable feed opening 3| and driven by any desirablemeans such as a belt and pulley 32, which is one arrangement that may beused for feeding the pulverized material to the classifier. This form offeed may be substituted for that described in connection with Fig. 1.

Returning to Fig. 3, it has been found advantageous in some instances toprovide the rotor and the opposite wall of the classification chamberwith facings of suitable material such as rubber. These facings areindicated in the drawing by the numerals 33 and 34. respectively. Thelower portion of the rubber faced rotor also may be provided with rubberimpellers or fins 35. The relatively rough surface (as compared topolished metal) thus provided on the rotor wall H has an increasedskin-drag efiect and sets more air in motion than the polished metalsurface consequently increasing the vortex action and the centrifugalthrow-out of the various particles ac-' cording to their masscharacteristics, while the stationary rubber facing 34 has a dampingeffect tending to stop the travel of the projected particles at therubber surface, so that the desired stratification becomes sharplydefined. The rubber facings also protect the parts of the classiflerfrom wear and lengthen the life of the classifier, in which theincreased skin-drag effect probably plays an important part.

Although not shown, it will be understood that any suitable form ofregulator may be inserted in the air inlet opening 20 to thus controlthe amount of aspirating air admitted at the bottom of the machine. Byso controlling the air the particle side delivered and collected can bedetermined because varying this factor varies the upward force actingagainst gravity, and the time 'the material remains in the classifierchamber.

To obtain a high degree of uniformity in particle size with-materialrequired in some industries, Fig. 6 illustrates diagrammatically onemethod and arrangement of apparatus for continuously obtaining accuracyin classificationof materials. A pair of classifiers, of the generalkind described above, are connected together in a manner such thatoversize and underslze particles are definitely eliminated from thefinal and changes may be made without departing from the fundamentalprinciples outlined. Accordingly, it is not intended to imposelimitations in the scope of the invention, except as defined in theappended claims.

I claim: i

1. A machine for classifying pulverized material containing particles ofdifferent sizes, comprising a cylindrical casing, a cylindrical rotorwithin said casing and concentric with and spaced from said casing toform a classifying chamber therebetween which is narrow as compared tothe diameter of said rotor, means for feeding the material .and agaseous medium to the classifying, chamber, means for driving saidrotorat high speed to maintain a vortex of said material in gaseoussuspension, means for causing the suspended material to rise in theclassifying chamber during'the vortex action, and a tapping port at adefinite level along the side of the casing through which particlw ofthe suspended material of a predetermined size pass from said chamber.

.2. A machine for classifying pulverized material containing particlesof diiferent sizes, comprising a cylindrical casing, a cylindrical rotorwithin said casing and concentric with and spaced from said casing toform a classifying chamber therebetween which is narrow as compared tothe diameter of said rotor, means for' feeding the material and agaseous medium to the classifying chamber, means for driving said rotorat high speed to maintain a vortex of said material in gaseoussuspension,. means for causing thesuspended material to rise in theclassifying chamber during the vortex action, and tapping ports atdifferent levels along the side of the casing through which particles ofsaid material of predetermined different sizes pass from said chamber.

3. A machine for classifying pulverized material containing particles ofdiflerent sizes, comprising a cylindrical casing, a cylindrical rotorwithin said casing and. concentric with and spaced from said casing toform a classifying chamber therebetween which is narrow-as compared tothe diameter of said rotor, means for feeding the material and a gaseousmedium to the classifying chamber, means for driving said rotor at highspeed to maintain a vortex of said material ingaseous suspension, meansfor causing the suspended material to rise in the classifying chamberduring the vortex action, an outlet at the top of the casing for removalof collectible flne particles of said material rising in said chamberadjacent the peripheral face of the rotor, and a tapping port at adefinite level along the side of the casing through which classifiedparticles of said material of a size larger than said fine particlespass from said chamber.

4. A machine for classifying pulverized material containing particles ofdifferent sizes, comprising a cylindrical casing, a cylindrical rotorwithin said casing and concentric with and spaced from said casing toform a classifying chamber'therebetween which is narrow as compared tothe diameter of said rotor, means for feeding the material and a gaseousmedium to the classifying chamber, means for driving said rotor at highspeed to maintain a vortex'of said material in gaseous suspension, meansfor causing the suspended material to rise in the classifying chamberduring the vortex action, an outlet at the top of the casing for removalof collectible fine particles of said material rising in said chamberadjacent the peripheral face of the rotor, and tapping ports atdifferent levels along the side of the casing through which classifiedparticles of said material of larger sizes pass from the classificationchamber.

5. A machine for classifying pulverized material containing particles ofdiiferent sizes, comprising a cylindrical casing,. a cylindrical rotorwithin said casing and concentric with and spaced from said casing toform a classifying chamber therebetween which-is narrow as compared tothe diameter of said rotor, means for feeding the material and a gaseousmedium to the classifying chamber at one end thereof, means for drivingsaid rotor at high speed to maintain a vortex of said material ingaseous suspension, means for causing the suspended material to rise inthe classifying chamber during the vortex action, and a tapping port ata definite level along the side of the casing through which classifiedparticles of material pass from said chamber, the classifying rotorbeing provided with impeller blades extending part Way along said rotoradjacent said feeding means only.

6. A machine for classifying pulverized material containing particles ofdifferent sizes, comprising a cylindrical casing, a cylindrical rotorwithin said casing and concentric with and spaced from said casing toform a classifying chamber therebetween which is narrow as com pared tothe diameter of said rotor, means for feeding the material and a gaseousmedium to the classifying chamber, means for driving said rotor at highspeed to maintain a vortex of said material in gaseous suspension, meansfor causing the suspended material to rise in the classifyi ing chamberduring the vortex action, and a tapping port at a definite level alongthe side of the casing through which classified particles of saidmaterial pass from said chamber, said feeding means including an openingthrough the casing beneath said tapping port and a connecting conduitsubstantially tangential to said classifying chamber.

7., A machine for classifying pulverized material containing particlesof different sizes, comprising a casing, a rotor concentric with andspaced from said casing to form therewith a classifying chamber, meansfor feeding the material and a gaseous medium to the classifyingchamber, means for driving said rotor at high speed to maintain a vortexof said materialin gaseous suspension, means for causing the suspendedmaterial to rise in the classifying chamber during th vortex action, atapping port at a definite level along the side of the casing throughwhich classified particles of material pass from said chamber, saidfeeding means including an opening through the casing beneath saidtapping port and a connecting conduit substantially tangential to saidclassifying chamber, and an exit opening in the periphery of saidchamber and adjacent the lower end thereof from which gravitatedmaterial is swept from the machine by the action of the rotor.

8. A machine for classifying pulverized material containing particles ofdifferent sizes, comprising a casing, a rotor concentric with and spacedfrom said casing to form therewith a classifying chamber, means forfeeding the material and a gaseous medium tothe classifying chamber,means for driving said rotor at high speed to maintain a vortex of saidmaterial in gaseous suspension, means for causing the suspended materialto rise in the classifying .chamberduring the vortex action, tappingports at different levels along the side of the casing through whichstratified particles of said material of predetermined different sizespass from said chamber, said feeding means including an opening throughthe casing beneath all of said tapping ports and a connecting conduitsubstantially tangential to said classifying chamber, and an exitconduit substantially tangential to said chamber and beneath the planeof said other opening.

9. A machine for classifying pulverized material containing particles ofdifferent sizes, comprising a .casing, a rotor concentric with andspaced from said casing to form therewith a classifying chamber, meansfor feeding the ma terial and a gaseous medium to the classifyingchamber, .means for driving said rotor at high speed to maintain avortex of said material in gaseous suspension, means for causing thesuspended material to rise in the classifying chamber during the vortexaction, tapping ports at different levels along the side of the casingthrough which stratified particles of said material of predetermineddifierent sizes pass from said chamber, said feeding means including anopening through the casing beneath all of said tapping ports and aconnecting conduit substan- 1 tially tangential to said classifyingchamber, and

'an exit conduit substantially tangential to said chamber and beneaththe plane of said other opening.

10. A machine for classifying pulverized material containing particlesof different sizes, comprising a casing, a smooth rotor having a smoothsurface concentric with and spaced from said and a port at the side ofthe casing communicatcasing to form therewith a classifying chamber,

an inlet for a gaseous medium at one end of said rotor, meanscommunicating with the other 'end of the rotor so constructed andarranged that said medium rises through the classifying chamber, meansfor feeding the pulverized material to the chamber, means for drivingthe rotor at high speed to maintain a vortex action and to intermix saidmaterial with the gaseous medium to form a suspension of dispersedparticles, and

ports at the side of the casing at different levels along theclassifying zone so that stratified particles of predetermined particlesizes respectively may be removed from the classifying chamber.

12. A machine for classifying pulverized material containing particlesof different sizes, comprising a cylindrical casing, a'vertical,cylindrical rotor within said casing and concentricwith and spaced fromsaid casing to form a classifying chambentherebetween which is narrow ascompared to the diameter of said rotor, an inlet for a gaseous medium atone end of said rotor and means communicating with the other end of therotor arranged so that said medium rises through the classifyingchamber, means forfeeding the pulverized material to the chamber, meansfor driving the rotor at high speed to maintain a vortex action and tointermix said material with the gaseous media to form a suspension ofdispersed particles, a port at the side of'the casing communicating withthe classifying chamber,

said port being located at a point intermediate the ends of said rotorand being adapted for the 'withdrawal from said chamber of stratifiedmaterial of a predetermined particle size, said casing having an outletport above the rotor, and a plate adjacent the top of the rotorinterposed between said outlet port and the classifying chamber, saidplate having an opening for passage of relatively small and collectibleparticles.

chamber therebetween which is narrow as compared to the diameterv ofsaid rotor, an inlet for a gaseous medium at one end of said rotor,means communicating with the other end of the rotor arranged so thatsaid medium rises through the classifying chamber, means for feeding thepulverized material to the chamber, means fordriving the rotor at highspeed to produce and maintain a vortex action and to intermix saidmaterial with the gaseous media to form a suspension of dispersedparticles, the lower peripheral portion only of' said rotor'beingprovided. with impeller blades to initiate the vortex action, the lowerportion of the casing adjacent said blades being inclined inwardly andupwardly.

14. A machine for classifying pulverized material containing particlesof different sizes, com- "prising a cylindrical casing, a vertical,cylindrical rotor within said casing and concentric with and spaced fromsaid casing to form a classifying ch mber therebetween which is narrowas compa ed to the diameter of said rotor, an inlet for a gaseous mediumat one end of said rotor, means communicating with the other end of therotor arranged so that said medium rises through the classifyingchamber, means for feeding the pulverized material to the chamber, meansfor drivingthe rotor at high speed to produce and maintain-a vortexaction and to intermix said material with the gaseous media to form asuspension of dispersed particles, the lower portion only of said rotorhaving inwardly and upwardly tapered impeller blades, and the lowerportion of said casing being similarly tapered.

15. A machine for classifying pulverized material containing particlesof different sizes, comprising a cylindrical casing, a vertical,cylindrical rotor'within said casing and concentric with and spaced'fromsaid casing to form a classifying chamber therebetween which is narrowas compared to the diameter of said rotor, an inlet for a gaseous mediumat one end of said rotor, means communicating with the other end of therotor arranged so that said medium rises through the classifyingchamber, means for feeding the pulverized material to the chamber, meansfor driving the rotor at high speed to produce and maintain a vortexaction and to intermix said material with the gaseous media to form asuspension of dispersed particles, the lower portion only of said rotorhaving upwardly and inwardly tapered impeller blades, the lower portionof said casing being also upwardly and inwardly tapered to cooperatewith said blades, and a discharge opening opposite said blades.

16. A machine for classifying pulverized material containing particlesof different sizes, comprising a cylindrical casing, a vertical,cylindrical rotor within said casing and concentric with and spaced fromsaid casing to forma classifying chamber therebetween which is narrow ascompared to the diameter of said rotor, means for feeding the materialand agaseous medium to the classifying chamber, means for driving saidrotor at high speed to maintain a vortex of said material in gaseoussuspension, means for causing the suspended material to rise in theclassifying chamber during the vortex action, and a tapping port at adefinite level along the side of the casing through which stratifiedparticles of material pass from said chamber, the portion of said casingabove the level of said port being enlarged and communicating therewith.

17. A machine for classifying pulverized material comprising astationary cylindrical casing, a concentric smooth walled cylindricalrotor within said casing and spaced therefrom a distance which is smallas compared to the diameter of the rotor, resilient covering materialupon opposed faces of said casing and rotor, means for feeding a gaseousmedium and pulverized material to the space between the casing androtor, outlets respectively for material of selected size and foroversize material, and blades constructed at least in part of resilientmaterial cooperating with said rotor to produce and maintain a vortexaction in the pulverized material and gaseous medium and to ejectoversize particles of matehaving a smooth wall except for a bladedportion at one end thereof, a rubber covering for the inner surface ofthe casing and for the opposed surface of the rotor, nieans for feedingmaterial to the space between the rotor and casing, an 'outlet from saidspace adjacent the end of the rotor opposite said bladed portion, andmeans for producing a current of air through substantially the entireextent of said space and through said outlet.

19. A machine for classifying pulver d material comprising a stationarycylind cal casing having a smooth rinner surface, a concentriccylindrical rotor within said casing and spaced radially therefrom adistance which is small as bladed portion, and means for producing acurrent of air through substantially the entire extent of said space andthrough said outlet.

' HENRY G. LYKKEN.

